Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2009
Publication Date: 1/1/2010
Citation: Keith, L.M., Zee, F.T. 2010. Guava diseases in Hawaii and the characterization of Pestalotiopsis spp. affecting guava. Acta Horticulturae. 849:269-275.
Interpretive Summary: In Hawaii, common guava (Psidium guajava L.) is found throughout the island at various elevations and under various environmental conditions. Guava is also one of the most vigorous and widespread plants in the tropics and is associated with many fruit rot diseases. Guava is commonly processed into puree and juice, thus disease can decrease its marketability. It is common to see leaf and fruit spots on guava in Hawaii. Identification and the proper management of the diseases are important for the successful cultivation of the crop. The objective of this work was to determine the most prevalent pathogens on guava in Hawaii and to determine if sources of host resistance to scabby canker exist in the available germplasm.
Technical Abstract: Guava (Psidium guajava L.), one of the most widely grown plants in the tropics, is very susceptible to disease which can decrease its marketability. Leaf and fruit spot diseases commonly occur on guava grown in Hawaii. A disease survey was conducted on more than 50 accessions grown at the USDA/ARS Tropical Plant Genetic Resource and Disease Research Unit in Hilo, Hawaii. The four main fungi isolated from leaves and fruit were Pestalotiopsis, Colletotrichum, Mucor and Guignardia. Disease symptoms of these fungi were visible on leaves without fruit present, and on the skin of young fruits (pinhead size) which progressed as fruits matured. The highest disease incidence by far (>85%) was for Pestalotiopsis spp. The main diagnostic symptoms were grey/light brown lesions surrounded by dark brown borders on leaves and brown, raised, corky, necrotic lesions on the exocarp of fruit. The Pestalotiopsis spp. were isolated, identified and characterized. Pathogenicity was demonstrated on wound-inoculated fruit and leaves by fulfilling Koch’s postulates. Potential sources of host resistance were identified in the germplasm. The importance of Pestalotiopsis as a guava pathogen and its cross-infection potential are discussed.